Helena Davis | 2025 I.S. Symposium

Name: Helena Davis
Title: Host Species Range Expansion as a Risk Factor of Polyvalent Phage Applications in Emerging Phage Therapeutic Techniques
Major: Biochemistry and Molecular Biology
Advisor: Stephanie Strand

Bacteriophages were first discovered and envisioned for antibiotic applications by Felix d’Herelle in the early 20th century. However, they fell out of favor when broad-spectrum antibiotics such as penicillin were popularized. However, with the emergence of multi-drug-resistant bacterial threats that broad-spectrum antibiotics are ineffective against, there has been a resurgence of interest in phage therapy. For the purposes of this study, monovalent phages are defined as phages which infect a single species of bacteria, while polyvalent phages can infect multiple species or even genera. A key property common to polyvalent phages is an abundance of hypervariable SNP sites in the genes coding for the tail fiber and tail tubular regions, two regions heavily involved in the phage binding to receptors on the surface of bacteria to infect them. While increased adaptability to resistance-mutations in bacterial receptor structures may seem beneficial, this property, which allows polyvalent phages to expand their “host-range”, or the number of species/genera they can infect, could make therapeutic applications more risk-prone, as many microbiotal bacteria serve a beneficial, symbiotic purpose, and here it is hypothesized that with the wrong mutation or combination of mutations in the phage, these “good bacteria” may be prone to cross-infection.

Posted in Symposium 2025 on May 1, 2025.